The present invention relates to systems and methods of compensating sensor error of a differential pressure sensor on an exhaust gas recirculation passage for a calculation of a flow rate of recirculated exhaust gas into a vehicle engine.
In compression-ignition engines, such as heavy-duty diesel engines, the intake air is typically cooled and compressed by using a turbo charger, to provide increased power density for the engine. Added flexibility in the compression of the intake air over a conventional turbo charger is often achieved by using a variable geometry turbo charger (xe2x80x9cVGTxe2x80x9d) which may be controlled by the engine""s electronic control module (xe2x80x9cECMxe2x80x9d) to supply varying amounts of turbo boost pressure to the engine, depending on various operating conditions. One system for controlling an engine having a VGT is disclosed in U.S. Pat. No. 6,000,221, issued to Church et al. on Dec. 14, 1999.
While designing engines to minimize the negative impact on engine fuel economy and durability, compression-ignition engine designers have also been challenged in designing engines to reduce NOx emissions. An engine is equipped with several sensors to allow the ECM to effectively reduce NOx emissions. However, sensors used in obtaining data to reduce NOx emissions typically include differing calibrations and error. As a result, the engine""s ECM may perform non-optimally in reducing NOx emissions, due to such differences.
It is an object of the present invention to provide for an improved method of compensating sensor error of a differential pressure sensor of an exhaust gas recirculation passage for a calculation of a flow rate of recirculated exhaust gas into a vehicle engine. The method includes providing data representing default output of the differential pressure sensor based on the coolant temperature of the engine and providing a predetermined threshold deviation of the default output. The method further includes determining the engine coolant temperature and an actual idle output of the sensor, when the engine is at an idle engine speed for a predetermined period time, and calculating an actual error value of the sensor based on observing the actual idle output of engine coolant temperature. The method further includes utilizing the actual error value in calculating the flow of the recirculated exhaust gas into the vehicle at off-idle conditions.
In another embodiment of the present invention, the method further includes determining the engine coolant temperature and an actual number of key-on output of the sensor, upon ignition of the engine. The method further includes signaling a key-on fault code and applying the default output at the respective coolant temperature to a calculation of the flow rate of recirculated exhaust gas into the vehicle engine, if the actual number of key-on output is greater than a first sum. Further, the method comprises signaling an ignition fault code and applying the default output at the respective coolant temperature to the calculation of the flow rate of the circulated exhaust gas into the vehicle engine, if the actual number of idle output is greater than a second sum.
It is another object of the present invention to provide an improved system for compensating sensor error of a differential pressure sensor on an exhaust gas recirculation passage for use in a calculation of a flow rate of recirculated exhaust gas into a vehicle engine. The system comprising an exhaust gas re-circulating valve mounted in the engine exhaust line for controllably diverting a selected portion of the exhaust gas for mixture with intake error, a temperature sensor mounted in the flow path of the engine coolant, and an obstruction in the flow path of the re-circulating exhaust gas. The system further includes a differential pressure sensor including a first pressure tab located for sensing the pressure of the recirculated exhaust gas upstream of the obstruction, and a second pressure tab located for sensing the pressure of the recirculated exhaust gas downstream of the obstruction, wherein the differential pressure sensor has outputs indicative of current differential pressure across the obstruction. The system further includes control logic for determining flow rate of the recirculated exhaust gas, wherein the control logic has a list of default output of the differential pressure sensor based on the coolant temperature of the engine and has a predetermined threshold deviation of the default output of the differential pressure sensor.
It is yet another object of the present invention to provide for still another improved system for compensating sensor error of a differential pressure sensor on an exhaust gas recirculation passage for use in a calculation of a flow rate of recirculated exhaust gas into a vehicle engine. The system includes a mechanism for providing data representing default output of the differential pressure sensor based on the coolant temperature of the engine and providing a predetermined threshold deviation of the default output, a mechanism for determining the engine coolant temperature and an actual idle output of the sensor, when the engine is at an idle engine speed for a predetermined period of time. The system further includes a mechanism for calculating an actual error value of the sensor based on observing the actual idle output and engine coolant temperature, and a mechanism for utilizing the actual error value in calculating the flow rate of the recirculated exhaust gas into the vehicle engine at off-idle conditions.